These two views of the right valve of a Ponderous Ark (Noetia ponderosa) show a large number of boreholes and dwellings made across that structure by the small bivalve known as Stimpson Chimney Clam, Rocellaria stimpsoni Tryon, 1861. Red lines connect external (left) and internal views of each borehole/dwelling. Read more about the curious boring habits of the Stimpson Chimney Clam here.
